With the death of Ernst Mach on February 19, 1916, one day after his seventy-eighth birthday, a question finally became explicit that had been looming for some time. It was as simple as it was fundamental: who, in the end, was this man, a scientist or a philosopher? The importance of this question for contemporaries can easily be gleaned from the obituaries that appeared in the weeks following Mach's death: one in the Physikalische Zeitschrift, written by Albert Einstein, and another in the Archiv für die Geschichte der Philosophie, written by Mach's former student Heinrich Gomperz. They both addressed this critical issue in plain words. Einstein stressed that Mach “was not a philosopher who chose the natural sciences as the object of his speculation, but a many-sided, interested, diligent scientist who also took visible pleasure in detailed questions outside the burning issues of general interest” (Einstein 1916, 104; translation cited in Blackmore 1992, 158). Gomperz in turn first emphasized the great loss science had experienced with Mach's death, asking subsequently whether “the suffering science is physics or philosophy?” (Gomperz 1916, 321). His answer broadly followed Einstein's conclusion; relying on Mach's own words, he reminded his readers that Mach never claimed to be a philosopher, but merely was looking for a viewpoint that transcended the disciplinary constraints of particular scientific activities.

Many debates have already taken place on the reliability of the results obtained by means of sphygmographs. The following remarks may contribute to clarify some still unsettled points.

In this paper, I argue that studying school textbooks is a fruitful way to investigate mathematical conceptions in different national contexts. These sources give access to the written production of an extended mathematical milieu whose members write for various audiences. By studying the case of late 1950s French and English textbooks issued for a growing audience of 11- to 15-year-old pupils, I show that a plurality of conceptions was projected at the time onto pupils and their teachers in both national contexts. I link this diversity to contemporaneous debates regarding mathematics teaching and argue that textbooks themselves have to be considered as active agents of such debates.

In some cases our sensory organs are no longer capable of rendering processes in the external world perceptible to us. Their inadequacy expresses itself, for example, in phenomena that involve the kind of expansion of space and time in which the conditions for summary perception are no longer at all present. The resources that aid our immediate sense perception in these circumstances will thus be charged with the task of expanding or diminishing space and time to the extent that the contiguity and succession of events is comprehensible to us. The microscope is thus essentially based upon the principle of spatial expansion, the map on that of spatial diminution. The pertinent contrivances for these purposes are largely derived from the graphic arts. How stereoscopy and instantaneous photography, which is based on temporal expansion, facilitate our perception! In spite of the multifarious applications of photography, one has yet to take the step of employing it in the opposite direction, namely as a means of temporal diminution. We demonstrate that phenomena that take place in too ephemeral and too rapid a succession for our eyes can, with the help of instantaneous photographs in series, be analyzed with our senses as the event passes in a comparatively longer time. Quite analogously, we could also compress into a small duration the moments of an event separated widely from one another in time and thereby give our perception an understanding of the nature thereof.

In spring 1888, an anonymous critic raised severe doubts about Ernst Mach's and Peter Salcher's studies, published one year before, on the processes in the air caused by very rapid projectiles. Paraphrasing the experiments for the French popular science magazine La Nature, the critic insinuated that the photographs upon which Mach and Salcher's argument were ostensibly based must have been of such low quality that they did not allow any well-founded conclusion. The critic did not deny the phenomena Mach and Salcher had presented in their article; he denied that the photographs taken in the course of the experiments could permit any observation of the phenomena. I take the resulting quarrel as a window into the actors’ ideas on the requirements of “good observations” and the role of technical devices in this case. In particular I enquire how the various arguments relate to Lorraine Daston's and Peter Galison's framing of photography as an emblem of “mechanical objectivity.” We will see that in the case under debate, actors considered naked-eye observation, observation by telescope and photography mainly with regard to the challenges of the particular research object.

The sphygmograph as designed and tested by Jules-Étienne Marey – an apparatus destined to write pulse tracings on paper – revolutionized medical diagnostics in the early 1860s. Since the accuracy with which this device registered and objectified the pulse was controversial from the outset, the young scholar Ernst Mach (soon to become a leading theoretician and philosopher) decided to thoroughly examine Marey's sphygmograph. The investigation led to the invention of an alternative, truly Machian, sphygmograph. Mach's sphygmograph had originated in the regime of theoretical and applied physics, whereas the instrument invented by Marey had been rooted in the regime of experimental physiology. This one type of instrument thus serves as the focal object of a comparative study of two antagonistic epistemological approaches to sphygmography.

It is undisputed that all scientific knowledge proceeds from sense perception. And the way in which sense perception is fostered by the graphic arts generally, and in particular by photography (stereoscopy included), likewise needs no further explanation here.